An air bag device, for example, an air bag device against a side collision has been conventionally structured to expand in its entirety at a time.
It has been known that the waist of a crew sitting down first comes into collision with a vehicle's door to be then subjected to an impact, and the chest of the crew subsequently comes into collision with the vehicle's door. However, when trying to sufficiently absorb energy at the time of the side collision, such a structure as described has turned out inadequate particularly for protection of only the waist, first and foremost, having therefore failed to provide a satisfactory countermeasure against the side collision.
There has been known an air bag device against a side collision (refer to Japanese Patent No. 2933894) developed under the circumstances, incorporating an air bag having two air-chambers integral with each other, comprising a lower air bag corresponding to the waist of a crew, on a side of the crew, facing a vehicle body, and an upper air bag corresponding to the chest of the crew, on the side of the crew, facing the vehicle body, wherein a partition wall provided between the upper air bag and the lower air bag has a pressure control valve interposed therebetween, thereby causing the lower air bag to be expanded ahead of the upper air bag.
With the above-described air bag device against the side collision, the air bag against the side collision expanded in a vertical direction from seat cushion side parts is first inflated up to the height of the waist of the crew, thereby protecting the waist of the crew, and continues to be spread out up to the height of the chest of the crew.
However, if attention is focused on not only the waist, and chest, but also on the head of the crew when using the air bag against the side collision, while there is, for example, the need for a portion of the air bag, corresponding to the waist, reaching a peak pressure before the elapse of 4 ms from expansion of the air bag against the side collision, and thereafter, being quickly reduced in pressure, thereby mitigating a repellent force of the air bag against the side collision, applied to the waist, a portion of the air bag, corresponding to the head, needs to keep pressure at a peak value even after the elapse of 12 ms to thereby securely hold the head, so that, in practice, it is necessary not only to differentiate simply in timing for expansion between the respective portions of the air bag against the side collision, but also to differentiate in pressures after the expansion between the respective portions of the air bag, corresponding to respective parts of the body of the crew. Nevertheless, with the conventional air bag device, it is impossible to differentiate in pressure between the upper air bag, and the lower air bag.
Accordingly, with the structure described, there is a problem in that the pressures of the respective portions of the air bag, after the expansion thereof, cannot be optimally adjusted so as to correspond to the respective parts of the body of the crew.
Accordingly, there has been proposed an air bag device (refer to paragraph numbers ┌0021┘, ┌0022┘ and FIG. 1 of JP 10-100827A) wherein a partition wall having a communicating part is provided inside a bag-like body of the air bag device, and while the bag-like body is partitioned into first and second chambers, that is, upper and lower ones, there is provided a check valve structured such that an edge of a thin film, at both ends thereof, is fixedly attached to the upper face of the partition wall in such a way as to cover the communicating part, and when gas of the lower chamber flows into the upper chamber, a midpoint part of the check valve is bulged upward in a arch-like state owing to pressure of the gas flowing from the lower chamber into the upper chamber through the communicating part, thereby releasing the check valve so as to allow the gas of the lower chamber to flow into the upper chamber, however, upon addition of out-flow pressure of the gas from the upper chamber to the lower chamber, the communicating part is blocked by the midpoint part of the check valve, thereby blocking out-flow of the gas from the upper chamber to the lower chamber.
With the air bag device described as above, however, there are the needs for separately fabricating the check valve, and attaching it to the partition wall in size large enough to allow the check valve to be attached thereto, causing problems such as an increase in a component count, inability of securing the communicating part in a shape requiring a small gas path, and so forth.
The present invention has been developed to solve those problems described above.
It is a first object of the present invention to effectively protect a crew by allowing plural air chambers to be differentiated in pressure with a simple structure in an air bag comprising plural air chambers needing different characteristics.
It is a second object of the present invention to prevent gas from back-flowing from a second air chamber to a first air chamber utilizing a cloth without needing components such as a pressure adjustment valve fabricated separately as made conventionally, reducing cost of an air bag device.
It is a third object of the present invention to effectively protect a body of a crew at the time of collision by providing a flow path of gas for expansion of the air bag.